This invention relates a transport device for wafers of varying diameters in connection with a semiconductor manufacturing apparatus. More particularly, the present invention relates to a transport device which can transport a wafer to the center of a reactor and also transport the wafer to a vacuum load lock system from the reactor without the need to change a wafer holder for wafers with diameters between 2 inches to 8 inches.
In general, various semiconductor wafers with diameters of 2 to 6 inches are used in semiconductor manufacture. Poisonous gas, such as silane (SiH.sub.4) and ammonia (NH.sub.3), is frequently used in such manufacture. At the same time, extremely small pattern formation is required in order to increase the density of semiconductor elements on the wafer. As a result, contamination on the wafer from small particles must be prevented as much as possible.
Accordingly, a vacuum load lock system is required in a highly efficient semiconductor manufacturing apparatus for contamination prevention caused by small particles and for prevention of leakage of poisonous gas. The wafer transport device is also required in this vacuum load lock system in order to transport the wafer to the reactor which is formed with a cassette or a wafer supply device.
Among the wafer devices which are presently used, a wafer transport device which utilizes a robotic arm is widely viewed as the most reliable system for operation in the inner part of the vacuum system and the one which introduces the fewest contamination particles. However, in such a device which takes advantage of the features of a conventional robotic arm, the diameter of the wafer used is fixed, and thus this device is of limited value. A robotic arm having variable diameter capacity can transport wafers to the center of the reactor and to the center of the vacuum load lock system but only by changing the wafer holder when the wafer diameter changes. This causes a decline in production efficiency and unduly complicates the manufacturing process.